1. Field of the Invention
The present invention relates to a measuring instrument for bringing a spindle into contact with a workpiece to measure the dimension of the workpiece based on the moving position of the spindle. More specifically, it relates to a measuring instrument having a body and a spindle provided to the body movable in the axial direction of the body, in which the spindle is brought into contact with the workpiece by moving the spindle in the axial direction to measure the dimension of the workpiece, the measuring instrument being capable of displaying measuring force.
2. Description of Related Art
A measuring instrument having a spindle movably provided to a body to be in contact with a workpiece for detecting a dimension of the workpiece such as, for instance, a micrometer, also has a ratchet mechanism for bringing the spindle into contact with the workpiece at a constant force as well as a thimble for advancing and retracting the spindle in the axial direction thereof.
During measurement, after placing the workpiece between the anvil and the spindle, the thimble is rotated to move the spindle toward the workpiece, thereby sandwiching the workpiece by the anvil and the spindle. Subsequently, when hand is released from the thimble and a knob of the ratchet mechanism is rotated, the ratchet mechanism is freely rotated when more than a predetermined force is applied to the spindle, so that the measurement can be conducted at a constant measuring force.
In such a measuring instrument having the spindle to be in contact with the workpiece to measure the dimension of the workpiece, since the abutting force when the spindle is in contact with the spindle, i.e. the measuring force, exerts large influence on the measurement results, appropriate measuring force in accordance with the material and configuration of the workpiece is strongly desired.
However, though the constant measuring force can be maintained during measurement by the conventional measuring instrument, it is practically difficult to change the measuring force in accordance with the material and configuration of the workpiece.
An object of the present invention is to provide a measuring instrument capable of measuring a workpiece with the most suitable measuring force in accordance with the material and configuration of the workpiece.
In the present invention, a biaser and a biasing force indicator for checking the biasing force of the biaser are used to obtain the constant measuring force.
A measuring instrument according to the present invention includes: a body; a spindle provided to the body movably in an axial direction thereof, the spindle being moved in the axial direction to contact to a workpiece for measuring the dimension of the workpiece based on a moving position of the spindle; a sleeve provided to the body movable in the same direction as the moving direction of the spindle and stoppable at a desired position; a connector for connecting the sleeve and the spindle and allowing a relative movement of the sleeve and the spindle by a predetermined stroke in the moving direction; a biaser accommodated in the sleeve for biasing the spindle through the connector in a direction to abut to the workpiece; and a biasing force indicator for indicating a biasing force of the biaser.
According to the above-described measuring instrument, when the sleeve is moved in the axial direction of the spindle during measurement, the sleeve, the biaser, the connector and the spindle are moved in the same direction in a body. After the distal end of the spindle touches the workpiece, when the sleeve is further moved in the same direction, since the spindle cannot be moved, the biaser is gradually compressed. The force for the biaser to bias the spindle, in other words, the measuring force, is an addition of the force increasing in proportion to the compression to the preload, which is displayed on the biasing force indicator.
Accordingly, the measurement can be conducted under the most appropriate measuring force in accordance with material and configuration of the workpiece while checking the measuring force indicated by the biasing force indicator. In other words, when the material of the workpiece is soft, the workpiece can be measured with minute measuring force and a number of workpiece can be measured always under constant measuring force.
In the above, the sleeve may be manually moved, or may be driven by a release, lever, rack and pinion, motor, etc. However, the sleeve may preferably be driven by the below-described thimble.
The connector may have one end fixed to either one of the spindle and the sleeve and the other end being movably connected to the other one of the spindle and the sleeve by a predetermined stroke. Alternatively, both ends may be movably connected to the spindle and the sleeve by a predetermined stroke.
Any biaser capable of biasing the spindle in a direction to abut to the workpiece may be used. However, helical pressure spring may preferably be used.
In the present invention, a biasing force adjuster for adjusting the biasing force of the biaser may preferably be screwed to the sleeve.
According to the measuring instrument, when the screwing position of the biasing force adjuster screwed to the sleeve is changed, since the distance from the biasing force adjuster to the connector changes, the compression of the biaser accommodated therebetween changes. Accordingly, the preload can be changed with a simple arrangement.
In the present invention, the biasing force indicator may preferably include: a scale rod provided to the connector penetrating the biasing force adjuster; and a scale formed along a longitudinal direction of the scale rod at a predetermined interval.
According to the above measuring instrument, when the preload is changed by changing the screwing position of the biasing force adjuster relative to the sleeve, the distance from the connector to the biasing force adjuster (i.e. the compression of the biaser) changes. Then, since the projection of the scale rod from the biasing force adjuster changes, the compression of the biaser, i.e. the measuring force can be read by reading the scale formed on the scale rod. Accordingly, the preload can be adjusted while looking at the scale, or the measurement can be conducted under a desired measuring force.
In the present invention, the biasing force indicator may preferably include: a threaded shaft provided to the connector penetrating the biasing force adjuster and having an external thread on an outer circumference thereof; a nut screwed to the threaded shaft and provided to the sleeve rotatable and immovable in the axial direction; and an index fixed to the nut.
According to the above measuring instrument, after bringing the spindle into contact with the workpiece, when the sleeve is further rotated in the same direction, the connector and the sleeve (or the biasing force adjuster) are relatively displaced. Then, since the threaded shaft and the nut are relatively displaced in accordance with change in the compression of the biaser, the nut is rotated, i.e. the index is rotated. Accordingly, the compression of the biaser, i.e. the measuring force can be read by the rotary angle of the index, thereby conducting measurement under desired measuring force while observing the rotary angle of the index.
In the above, a graduation plate having an angle scale indicating a rotary angle of the index may be attached to the sleeve side for accurately reading the rotary angle of the index.
In the present invention, the biasing force indicator may preferably include: a detection switch for detecting that the spindle and the sleeve approach with each other by a predetermined distance; and a display for displaying an actuation of the detection switch.
According to the above measuring instrument, after the spindle is in contact with the workpiece during measurement, when the sleeve is further moved in the same direction, the spindle and the sleeve are relatively displaced. Then, the compression of the biaser changes. At this time, when the spindle and the sleeve approach with each other by a predetermined distance, the detection switch is actuated, which is displayed on the display. Accordingly, the attainment of a predetermined compression of the biaser, i.e. attainment of a predetermined measuring force, can be read by the indication on the display, so that the measurement can be conducted always at a constant measuring force.
In the above, the detection switch may include an electrode spring provided on either one of the spindle and the sleeve and an electrode provided to the other one of the spindle and the sleeve corresponding to the electrode plate spring.
In the present invention, a position detection indicator for detecting the moving position of the spindle as an electric signal and for digitally displaying the moving position of the spindle based on the detected result may preferably be provided, in which an indicated value of the position detection indicator is held when the detection switch is actuated.
According to the measuring instrument, the indicated value on the position detection indicator is automatically held when the compression of the biaser reaches a predetermined value, so that usability can be enhanced without requiring attention to the over-feed of the sleeve.
In the present invention, the biasing force indicator may preferably include: a force sensor provided between the connector and the biaser; and a measuring force indicator for displaying a magnitude of a force detected by the force sensor.
According to the above measuring instrument, since the force in accordance with the compression of the biaser is directly detected by the force sensor and is displayed on the measuring force indicator, the measuring force can be directly checked, so that the measurement under a desired measuring force can be more accurately conducted.
In the above, though the magnitude of the force displayed on the measuring force indicator may be indicated as a numeral, or alternatively as a bar graph. When the magnitude is displayed as a bar graph, the compressing process of the biaser can be visually checked, so that the sleeve can be easily stopped at a desired position.
In the present invention, the sleeve may preferably be provided to the body in a manner unrotatable and movable in the axial direction and may preferably be screwed to a thimble rotatably provided at a predetermined position of the body.
According to the above measuring instrument, when the thimble is rotated, the sleeve screwed thereto is movable in the axial direction and unrotatable relative to the body and thus is moved in the axial direction. Accordingly, by rotating the thimble, the sleeve can be minutely moved by a predetermined amount and can be stopped at any desired position.
In the present invention, an anvil opposing to the spindle for holding the workpiece against the spindle may preferably be provided to the body, and a holder for holding the workpiece against the anvil on both sides of the anvil sandwiching an axis line of the spindle may preferably be rotatably provided on the anvil side of the body.
According to the above measuring instrument, the workpiece can be held by the anvil and the holder and, under the condition, the spindle can be brought into contact with the workpiece for measurement. Accordingly, even a workpiece of small rigidity such as thin wire and of rolling shape such as a pin is to be measured, the workpiece can be stably held between the anvil and the holder, so that measuring operation can be easily and accurately conducted.
In the present invention, a preload indicator for indicating a preload of the biaser adjusted by screwing the biasing force adjuster may preferably be provided.
According to the measuring instrument, since the preload of the biaser is displayed by the preload indicator, the screwing position of the biasing force adjuster can be adjusted while checking the indication. Accordingly, the preload of the biaser can be accurately adjusted.
In the present invention, the preload indicator may preferably include a scale provided on the outer circumference of the biasing force adjuster along the axial direction.
According to the above measuring instrument, when the preload of the biaser is adjusted while adjusting the screwing position of the biasing force adjuster, since the position of the scale provided on the outer circumference of the biasing force adjuster along the axial direction relative to the sleeve, the preload of the biaser can be read by the scale. Accordingly, the preload indicator can be constructed with a relatively simple arrangement of providing scale along the axial direction on the outer circumference of the biasing force adjuster.
In the present invention, the preload indicator may preferably include: a display cylinder provided on an outer circumference of the biasing force adjuster in a manner capable of adjusting rotation and position thereof along the axial direction; and a scale provided on the outer circumference of the display cylinder along the axial direction.
According to the above arrangement, the standard scale of the display cylinder can coincide with a reference position by adjusting rotation or position in the axial position of the display cylinder having the scale relative to the outer circumference of the biasing force adjuster. Accordingly, even when there is dispersion in producing the biaser, the standard scale can be made consistent with the reference position without requiring special processing and adding new component.
In the present invention, a cover for covering the biasing force adjuster may preferably be detachably provided to the body.
According to the above measuring instrument, since the window since the window for exposing the scale is provided to the cover, the scale can be visually checked through the window. In other words, the scale can be visually checked while preventing fluctuation of the screwing position of the biasing force adjuster on account of contact to the biasing force adjuster.
In another aspect of the present invention, in order to obtain a constant measuring force, a measured value when a constant measuring force is obtained may be held.
A measuring instrument according to another aspect of the present invention includes: a body; a spindle provided to the body movably in an axial direction thereof, the spindle being moved in the axial direction to contact to a workpiece for measuring the dimension of the workpiece based on a moving position of the spindle; a digital display for digitally displaying the moving position of the spindle; a measuring force detector for detecting a measuring force for the spindle to press the workpiece; and an indication holder for holding a value indicated on the digital display when the measuring force detected by the measuring force detector reaches a predetermined value.
According to the above measuring instrument, after bringing the spindle into contact with the workpiece while moving in the axial direction, when the spindle is further pressed, the measuring force for the spindle to press the workpiece is detected by the measuring force detector. When the detected measuring force reaches a predetermined measuring force, the indicated value on the digital display is held. Accordingly, the measurement can be conducted under the most appropriate measuring force in accordance with material and shape of the workpiece.
In the above aspect of the present invention, the measuring force detector may preferably include: an index rotatably provided to the body; a movement converting mechanism for converting a measuring force for the spindle to press the workpiece into a rotary motion of the index; and a detection switch for detecting a predetermined amount of displacement of a part of the movement converting mechanism or the index to transmit a hold command to the indication holder.
According to the above measuring instrument, the measuring force for the spindle to press the workpiece is converted to the rotation of the index by the movement converting mechanism to be displayed. When the part of the movement converting mechanism or the index displaces for a predetermined amount, the indication holder holds the indicated value by the command from the detection switch, so that the measurement can be conducted under the most appropriate measuring force in accordance with material and shape of the workpiece.